Expandable interbody spacer device

ABSTRACT

An expandable interbody spacer ( 10 ) is provided that includes a pair of oppositely facing endplate components ( 20, 40 ) and an interior component that includes one or more vertically extending stacks of arranged C-clip members ( 70 ) radially surrounding one or more bosses ( 30 ) protruding interiorly from one of the endplates, wherein the size and configuration of the bosses and the C-clip members are designed to allow the incremental expansion of expandable interbody spacer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/921,242 filed on Sep. 7, 2010, which is the U.S. National Phase ofPCT Application No. PCT/US2009/036148, filed on Mar. 5, 2009, and claimsthe benefit of U.S. Provisional Application No. 61/034,713 filed on Mar.7, 2008, entitled “EXPANDABLE INTERBODY SPACER DEVICE,” the contents ofeach application are incorporated in their entirety by reference herein.

BACKGROUND OF THE INVENTION

Interbody fusion spacers are utilized to restore physiological spacebetween two adjacent vertebrae and to maintain the space while fusionoccurs between the adjacent vertebrae. The surgeries used to place suchspacers can be painful for the patient and the size of the incision andapproach channel provides challenges. It is desirable to develop aninterbody spacer that promotes fusion while minimizing the size of theincision required for implantation of the spacer. An interbody spacerthat assumes a collapsed configuration and subsequently deploys into anexpanded configuration within the disc space may enable fusion whilereducing the size of the required surgical incision. The surgicalprocedure utilized with such a spacer may also permit a surgeon todistract and size the disc space with the spacer itself as opposed tousing multiple separate instruments for distraction. It would beadvantageous to insert a relatively small spacer through a relativelysmall opening and expand the spacer to fit the disc space, or disc andvertebral space, appropriately. In this manner the surgical incision maybe relatively small while the anterior column height of the spine can berestored.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention an expandableinterbody implant, spacer or corpectomy device (interchangeably referredto as a spacer, implant or corpectomy device) for implantation betweenvertebra has a collapsed condition and an expanded condition. The spacermay comprise a superior or top component having an external surface forcontacting at least a portion of one vertebrae, and an inferior orbottom component having an external surface for contacting at least aportion of another vertebrae. The superior and inferior componentspreferably are moveable relative to each other so that the spacer maymove between the collapsed condition and the expanded condition.Preferably at least one boss member is positioned between and moveablerelative to at least one of the superior component and interiorcomponent. The boss member may include a side surface and a distal endsurface. One or more expandable clip members are preferably stacked oneon top of the other to form at least one stack of clips, wherein eachclip member preferably has a top surface, a relaxed position, adeflected position, and defines a space.

Preferably, the boss member passes through the space in the clip memberwhen the clip member is in the deflected position and the clip memberpreferably interferes with the movement of and does not permit the bossmember to pass through the space when the clip member is in the relaxedposition. Preferably each of the clip members in the stack deflects in aseries to the relaxed position as the distal end surface of the bossmember passes a top surface of each of the clips as the spacer expands,thereby allowing the spacer to expand in predefined increments.

Preferably all the clip members in the spacer are in the deflectedposition when the spacer is in the collapsed position. The clip membersmay have integral, resilient and elastically deflectable arms that moveupon application of a force. The clip members may be formed of a singlepiece of material and integrally connected. The spacer may have morethan one stack of clip members, each stack preferably comprising aplurality of clip members.

The superior component of the spacer preferably includes at least oneboss member extending toward the inferior component and the inferiorcomponent preferably includes at least one post member extending fromthe inferior component toward the superior component, or vice versa. Thepost member is preferably associated with the boss member such that thepost member may telescope with respect to the boss member as the implantexpands and collapses. The spacer may have one or more boss members, oneor more post members and one or more stacks of clip members. The bossmember(s) may have a recess and the post member(s) may move within therecess as the implant moves between the collapsed and expandedconditions. The clip members may have resilient arms that expand orcollapse upon application of a force. The arms of the resilient clipmembers may be circularly shaped, C-shaped, U-shaped, Y-shaped, orV-shaped, or have other shapes. The clip members may be secured to,connected to, integral with or unconnected to the inferior component.

The plurality of stacks of clip members may be connected by a centralmember located between the plurality of boss members. The plurality ofstacked resilient clips may form one or more separate stacks ofresilient clip members, each stack of clip members being associated witha different boss member. The clip members may be substantially flat andrelatively uniform in thickness. Alternatively, the clip members mayhave a non-uniform thickness, such as, for example, a wedge shape, andmay alternatively or in addition have a curved surface. The clip membersmay be shaped or otherwise configured and connected in a manner toprovide an angle of lordosis or lordotic curve, or to provide an angleof kyphosis or kyphotic curve. The superior and inferior componentsinclude edges along their perimeter and the separately stacked clipmembers may be located between the boss members and perimeter edges ofthe superior and inferior components. The boss members and the postmembers are preferably cylindrically-shaped.

The clip members preferably move to a relaxed position underneath theboss member as the distal end of the boss member passes the top surfaceof the clip member and supports the superior component when subjected toaxial compression. The clip members are preferably configured andarranged so that they are in compression when axial loads are applied tothe spacer. It is also possible to load the clips in shear and inbending. The clip members may have arms that are expanded and move awayfrom each other when the clip member is changed to the deflectedposition such that the space defined by the clip member is larger.Alternatively, the clip members may have arms that deflect inwardly whenthe clip members are changed to the deflected position and the armsexpand to the relaxed position.

In another embodiment, an expandable interbody spacer includes a pair ofoppositely facing endplate components and an interior component thatincludes one or more vertically extending stacks of arranged C-clipmembers radially surrounding one or more bosses protruding interiorlyfrom one of the endplates. The bosses and the c-clip members preferablyare designed to allow incremental expansion of the expandable interbodyspacer.

The spacer may further include a stop mechanism to limit the expansionof the spacer. Other features and configurations are contemplated andwill be apparent to one having skill in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments of the application, will be better understood whenread in conjunction with the appended drawings. The drawings, examplesand embodiments described within this specification are for the purposesof describing and enabling the best mode of the preferred expandableinterbody spacer and the preferred method of implanting the expandableinterbody spacer of the present invention and are to be understood asillustrative and exemplary of structures, features, aspects and methodsof using the present invention and not as limiting the scope of theinvention. It should be understood that the application is not limitedto the precise arrangements and configurations shown. In the drawings:

FIG. 1 illustrates a top perspective, partially exploded view of anexpandable interbody spacer, implant, or corpectomy device in accordancewith a first embodiment of the present invention;

FIG. 2 illustrates a top perspective view of the expandable interbodyspacer of FIG. 1 in a collapsed configuration;

FIG. 3 illustrates a top perspective view of the expandable interbodyspacer of FIG. 1 in a partially expanded configuration;

FIG. 4 illustrates a side perspective view of an expandable interbodyspacer in accordance with a second embodiment of the present invention;

FIG. 5 illustrates a top perspective view of inferior and intermediarycomponents of the expandable interbody spacer shown in FIG. 4;

FIG. 6 illustrates a bottom perspective view of a superior component ofthe expandable interbody spacer shown in FIG. 4;

FIG. 7 illustrates a top perspective view of a third embodiment of anexpandable interbody spacer in accordance with the present invention;

FIG. 8 illustrates a side perspective view of the expandable interbodyspacer shown in FIG. 7;

FIG. 9 illustrates a front perspective view of a fourth embodiment of anexpandable corpectomy device in accordance with the present invention,with portions shown in phantom for clarity;

FIG. 10 illustrates a front perspective view of the expandablecorpectomy device shown in FIG. 9 in a collapsed condition;

FIG. 11 illustrates a front perspective view of the expandablecorpectomy device shown in FIG. 10 in a partially expanded condition;

FIG. 12 illustrates a side elevational view of a stack of clip membersfor use in the expandable corpectomy device shown in FIG. 9;

FIG. 13 illustrates a top perspective view of the stack of clip membersshown in FIG. 12;

FIG. 14 illustrates a front perspective view of the stack of clipmembers shown in FIG. 12;

FIG. 15 illustrates a top plan view of an alternative embodiment of astack of clip members;

FIG. 16 illustrates a cross sectional end view of an alternativeembodiment of a boss member for use with the expandable interbody spacerof FIG. 1;

FIG. 17 illustrates the stacked clip members of FIG. 15 interacting withthe boss member of FIG. 16;

FIG. 18 illustrates an alternative embodiment of a stack of clip membersand a boss member;

FIG. 19 illustrates a top perspective, partially exploded view of amechanical ratcheting, expandable interbody spacer or expandablecorpectomy device in accordance with another embodiment of the presentinvention;

FIG. 20 illustrates a side elevational view of a mechanically expandableinterbody spacer in accordance with another embodiment of the presentinvention;

FIG. 21 illustrates a cross-sectional view of the expandable interbodyspacer of FIG. 20 in a collapsed position, taken along line 21-21 ofFIG. 20;

FIG. 22 illustrates a cross-sectional view of the expandable interbodyspacer of FIG. 20 in an expanded position, taken along line 21-21 ofFIG. 20;

FIG. 23 illustrates a top perspective view of a mechanical ratcheting,expandable interbody spacer in accordance with yet another embodiment ofthe present invention shown in a collapsed position;

FIG. 24 illustrates a top perspective view of the expandable interbodyspacer of FIG. 23, shown in an expanded position;

FIG. 25 illustrates a top perspective view of a mechanically expandableinterbody spacer in accordance with another embodiment of the presentinvention, wherein a superior component is removed for clarity;

FIG. 26 illustrates a side elevational view of the expandable spacer ofFIG. 25, shown in a collapsed position; and

FIG. 27 illustrates a side elevational view of the expandable spacer ofFIG. 25, shown in an expanded position.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments, implants, systems, kits, methods and examples describedwithin this specification are to be understood as illustrative andexemplary of the structures, features and aspects of the implant,system, kit and method of the present invention and not as limiting thescope of the invention. The features, structures, aspects and steps ofthe implant, system and method may be used singularly, alternatively ortogether as desired or appropriate. Certain terminology is used in thefollowing description for convenience only and is not to be used in alimiting manner or to be limiting in nature. The words “right”, “left”,“lower” and “upper” designate directions in the drawings to whichreference is made. The words “inwardly” and “outwardly” refer todirections toward and away from, respectively, the geometric center ofthe interbody spacer, the implant, the corpectomy device and designatedparts thereof. The words, “anterior”, “posterior”, “superior”,“inferior” and related words and/or phrases designate preferredpositions and orientations in the human body to which reference is madeand are not meant to be limiting. The terminology includes theabove-listed words, derivatives thereof and words of similar import.While the expandable spacer embodiments may be described as being placedin the spine, and more specifically as being placed in a spinal discspace between vertebrae, or as a replacement for both vertebra andspinal discs, as may be appropriate and desired, the spacer may haveadditional application in areas other than the spine, such as, forexample, long bones, other bones, soft tissue and as a spacer innon-medical applications.

Referring to FIGS. 1-3, a first embodiment of an expandable interbodyspacer 10 includes a superior component 20 and an inferior component 40,each of which includes an endplate 22, 42 that provides a contactsurface 24, 44 for engaging adjacent vertebra V in an implantedposition. The expandable interbody spacer 10 is preferably mountedbetween the adjacent vertebrae V and expanded to restore disc height ata damaged disc segment. In the first embodiment, the endplates 22, 42 ofthe superior component 20 and the inferior component 40 may include aseries of teeth, ridges, spikes, keels, and/or surface texturing,generally shown at 26, 46, to increase the coefficient of frictionbetween the endplates 22, 42 of the expandable interbody spacer 10 andthe adjacent vertebrae V, or to otherwise provide a mechanism for theendplates 22, 42 to engage the vertebrae V, thereby resisting movementof the interbody spacer 10 when inserted between adjacent vertebrae V.Further, the endplates 22, 42 may include a surface texturing or coatingto assist or promote bony in-growth or on-growth between the vertebralendplates and the implant endplates 22, 42 to further secure the spacer10 in position.

The superior component 20 of the first embodiment include two bossmembers 30, but is not so limited and may include a single or more thantwo boss members 30, protruding from an inferior surface 28 toward theinferior component 40 in an assembled configuration. The boss members 30include a side surface 32 and a distal end surface 34. The inferiorcomponent 40 preferably includes two post members 50, but is also not solimited and may include a single or more than two post members 50,extending from a superior surface 48 toward the superior component 20 inthe assembled configuration. Each of the post members 50 are operativelyassociated with the bosses 30 so that the boss members 30 are axiallytranslatable relative to the post members 50 in the assembledconfiguration. The bosses 30 and the post members 50 are not limited tobeing arranged in the described and illustrated manner and may bearranged in an opposite manner or may be otherwise constructed to permitgenerally linear or axial movement of the superior component 20 towardand/or away from the inferior component 40. In addition, the bossmembers 30 and post members 50 may be arranged in a manner to permitangular or rotational movement of the superior and inferior components20, 40 relative to each other such that the components 20, 40 may bemoved toward and away from each other at the direction of a surgeon oruser.

The expandable interbody spacer 10 of the first embodiment furtherincludes one or more clips 70. The clips 70 are preferably stacked oneatop the other between the superior and inferior components 20, 40 inthe assembled configuration. The clips 70 are preferably constructed ofa resilient material and include resilient arms 74, 76 that are flexibleand define a space 75 therebetween. The resilient arms 74, 76 alsodefine an opening 78 between the distal ends 77, 79. The arms 74, 76 mayelastically flex or move so that the space 75 and opening 77 can beenlarged or decreased. The stacked clips 70 may be integrally formedsuch that at least a connecting portion 72 continuously joins theentirety of the stacked clips 70 and the clips 70 may be fabricated fromthe same piece of material. The stacked clips 70 may alternatively befabricated from several pieces of material or may be independently foundand disposed or secured one on top of the other. The stacked clips 70 ofthe first embodiment are comprised of individual clip members 70 a, 70b, 70 c, 70 d independently stacked between the post members 50. Eachclip member 70 a, 70 b, 70 c, 70 d preferably has a non-deflected state(FIG. 1), also referred to as a relaxed position, in which the space 75of each clip member 70 a, 70 b, 70 c, 70 d is a first size that isdifferent than when the clip members 70 a, 70 b, 70 c, 70 d are moved tothe deflected state (FIG. 2), also referred to as a deflected position.In the first embodiment, the clips 70 in the deflected state areexpanded so that the space 75 is larger in comparison to the size of thespace in the relaxed position. The clips may be expanded throughinteraction with the side surfaces 32 of the boss members 30.Alternatively, the clips 70 could be deflected inwardly such that thespace 75 is smaller in the deflected state in comparison to the size ofthe space 75 in the relaxed position.

The stacked clips 70 are preferably disposed or secured to the inferiorcomponent 40 such that the clip members 70 a, 70 b, 70 c, 70 d areproximate both the bosses 30 and the post members 50 in the assembledconfiguration (FIGS. 2 & 3). The stacked clips 70 may alternatively beunconnected to either the superior or inferior component 20, 40. Whenthe expandable interbody spacer 10 is in a fully collapsed state (FIG.2), the bosses 70 are disposed interior to and in the space 75 of theclip members 70 a, 70 b, 70 c, 70 d and the clips 70 assume theirdeflected or expanded state due to being deflected outward by the bosses30. An instrument (not shown), such as a spreader instrument, can beused to move the superior component 20 relative to the inferiorcomponent 40, by grasping and urging the superior and inferiorcomponents 20, 40 away from each other. As the superior component 20 ismoved away from the inferior component 40, the clip members 70 a, 70 b,70 c, 70 d sequentially deflect inwardly as the distal end surface 34passes upper surfaces of each individual clip member 70 a, 70 b, 70 c,70 d to a position underneath the bosses 30. Depending upon the numberof individual clip members 70 a, 70 b, 70 c, 70 d, the expandable spacer10 may be positioned in a range of incrementally expanded sizes todistract a collapsed disc-space and restore height thereto.Physiological load is borne by the expandable interbody spacer 10 as itexperiences axial compression through the bottom facing or end surfaces34 of the bosses 30 onto the topmost deflected clip members 70 a, 70 b,70 c, 70 d or directly onto the inferior component 40, depending uponwherein the distal end surface 34 is positioned.

The boss members 30 of the first embodiment are cylindrically-shaped andhollow. Each of the boss members 30 include a recess or cavity 35 formedtherein with an opening 33 to accept the post members 50 and an opening36 exposed at the superior endplate 22.

The post members 50 of the first embodiment are cylindrically-shaped andmay be hollow or solid. The outside diameter of the post members 50 arepreferably slightly smaller than the diameter of the cavity 35 in theboss members 30 so that the post members 50 are slidably received withinthe boss members 30. Accordingly, the boss members 30 are axiallytranslatable up and down relative to the cylindrical post members 50. Asthe implant 10 expands in height, the superior component 20 moves awayfrom the inferior component 40 and the boss members 30 move relative tothe post members 50.

In the first embodiment, the stacked resilient clips 70 are comprised ofa pair of oppositely-facing C-shaped clips 70 joined together by aconnecting portion 72. The clips 70 are preferably secured to theanterior component 40 and each clip member 70 a, 70 b, 70 c, 70 dsurrounds at least a portion of one of the post members 50. Morespecifically, the post members 50 extend between the arms 74, 76 of theclip 70 and through the space 75. The resilient C-clips 70 may be formedintegrally with the anterior component 40 and a gap or space 85 ispreferably left between the exterior surface of the post member 50 andthe interior surface of the resilient clip arms 74, 76.

Specifically, in the first embodiment, the stacked C-clips 70 arecomprised of four C-clips 70 a, 70 b, 70 c, 70 d stacked on the inferiorcomponent 14. With the implant in the collapsed position as shown inFIG. 2, the boss members 30 slide down over the post members 50. Theoutside diameter, shape, size and/or configuration of the boss members30 is slightly larger than the space 75 when the clip members are in therelaxed position such that in order to permit the boss member to slidedown over the post members, the arms of each pair of the four resilientclips 70 a, 70 b, 70 c & 70 d are expanded to the expanded state(deflected state) or expanded position (deflected position) where thearms 74, 76 permit the boss members 30 to pass through. The implantpreferably is placed in the desired position in bone while in thecompletely collapsed position. With the implant in position, adistractor preferably is used to expand the implant. In use, thedistractor moves the superior component 20 away from the inferiorcomponent 40, which in turn moves the boss members 30 relative to thepost members 50. As the boss member 30 moves past the top edge 71 a ofthe first clip 70 a, the resilient arms 74 a, 76 a are no longer held inthe expanded position and move to the relaxed position where the topsurface 73 a of the resilient clip 70 a is positioned underneath thedistal end surface 34 of the boss member 30. If expansion of the implantcontinues, the boss member 30 continues to move relative to the postmember 50 until the distal end 34 of the boss member moves past the topedge 71 b of the second clip 70 b whereupon the resilient arms 74 b, 76b move to the relaxed position where the top surface 73 b of theresilient clip 70 b is positioned underneath the distal end surface 34of the boss member 30 as shown in FIG. 3. In FIG. 3, the stacked C-clips70 are arranged such that the third and fourth clips 70 c, 70 d remainin the expanded state pressing against external side surfaces 32 of thebosses 30, while the first and second clips 70 a, 70 b are in thenon-expanded state, or relaxed position, generally blocking orpreventing the bosses 30 and the superior component 20 from movingtoward the inferior component 40, thereby maintaining at least theillustrated distance between the contact surfaces 22, 42 and anyadjacent vertebrae that the expandable interbody spacer 10 is positionedbetween.

The expandable implant 10 will maintain its height because anycompressive force exerted on the end plates 22,42 is transmitted to theboss members 30, which transmits such forces to the resilient clips 70located beneath the bosses 30, which transmits the force to the inferiorcomponent 40. Preferably the clip members and implant design areconfigured and arranged so that the clip members are in pure compressionwhen axial loads are applied to the implant. Alternatively oradditionally, the clip members may be loaded in shear, bending or both.

While the embodiment of FIGS. 1-3 show four stacked, resilient clips itwill be appreciated that more or less resilient clips may be included topermit more or less of a height differential between the fully expandedand fully collapsed position. For example, the implant may only utilizeone clip, or a plurality of clips as shown in FIGS. 1-3. The clipmembers may be relatively flat and relatively uniform in thickness.Alternatively or additionally, the clip members may have a non-uniformthickness, such as, for example, a wedge shape, and may alternatively oradditionally have a curved surface. The clip members may be shaped orotherwise configured and connected in a manner to provide an angle oflordosis or lordotic curve, or to provide an angle of kyphosis orkyphotic curve.

The thickness of the resilient clips preferably determines theincrements of height adjustment of the implant. For example, if fouruniform clips of 2 mm in thickness are utilized, the implant spacer willhave a total height adjustment range of 8 mm, in 2 mm increments. Theresilient clips all may be the same thickness, different thickness or amixture of different thickness where some clips have the same thicknessand others do not. The resilient clips in the embodiment of FIGS. 1-3are connected at the central portion of the clips and are positioned inthe center of the implant. The clips may be located in other areas ofthe implant and have different configurations. Moreover, while the clipsin FIGS. 1-3 are generally C-shaped and referred to as C-clips, (whichare aligned back to back to form a dog-bone shape), the clips may haveother shapes such as for example, U-shaped, Y-shaped, V-shaped,circularly shaped or other shapes.

Additionally, as shown in the embodiment of FIGS. 1-3, there may beincluded one or more protrusions on the superior or inferior component20, 40 that serve as a mechanical stop to prevent the expandableinterbody spacer 10 from expanding too far and disassembling. Forexample, the superior component 20 in the first embodiment includes amechanical stop 25 and the top most C-clip 70 d of the stacked C-clips90 includes an overhang 80 that engage each other in a fully extendedposition to prevent the expandable interbody spacer 20 from expandingtoo far and disassembling. The interbody spacer 10 is not limited toinclusion of the above-described mechanical stop 25 and overhang 80 andmay include alternative mechanisms to prevent disassembly of the spacer10 during expansion, or may not include such an overextension stop ordisassembly mechanism without significantly impacting the operation ofthe spacer 10.

The stacked C-clips 70 are not limited to being positioned on theinferior component 40 and may be formed integrally with the inferiorcomponent 40 such that the inferior component 40 and the stacked C-clips70 are one component. The stacked C-clips can be unconnected to eitherthe superior or inferior component, or may be connected or secured tothe superior component or integral with the superior component. Inaddition, the bosses 30 can be solid, not hollow, and the stackedC-clips 70 can be formed integral to the inferior component 40 orotherwise secured thereto, and the post members 50 may be unnecessary.While the bosses 30 have been illustrated as hollow with the postmembers inserted into the hollow cavity, the bosses 30 and post members50 can be arranged as side by side projections that translate relativeto each other and which may or may not be interconnected.

While the embodiment of FIGS. 1-3 has endplates that have a lengthgreater than twice the width and are generally configured for aposterior interbody fusion procedure where an implant is inserted oneach side of the spinous process, the principles can be applied todifferent shapes and configurations of spacers.

Referring to FIGS. 4-6, a second embodiment of an expandable interbodyspacer 110 includes two separate inwardly-facing single stacks 192, 194of C-shaped clips 170 and at least one axial bore 123 formed in itsendplates 122, 142 for graft packing. The axial bore 123 extends throughthe interbody spacer 110 due in part to the separation of the clips 170into two single and separate stacks 192,194 and the removal of thecentral connecting portions 72 of the first embodiment. The clips 170that are included in the expandable interbody spacer of the secondembodiment are slightly less round and the resilient arms 174, 176 havea generally V-shape. There are three clips 170 a, 170 b, 170 c in eachof the stacks 192, 194 in the embodiment of FIGS. 4-6. The clips in eachstack 192, 194 are integral and comprise a connecting portion 172 andresilient, flexible arms 174, 176 extending from the connecting portion172. The two clip stacks 192, 194 are positioned so the arms at leastpartially surround the post members 150 and the post members 170 passthrough the space 175 defined by the arms 174, 176. The stack of clips192, 194 preferably are secured to the anterior component 140. Theseparate stacks 192, 194 are positioned between the outer perimeter edgeof the end plate 122, 142 and the post members 150.

The superior component 120 as shown in FIG. 6 has a single unitary bossmember 130. The space 175 defined by the arms 174, 176 of the clips 170in the non-radially expanded condition, or relaxed position, is toosmall to permit the boss member 130 to pass through, and the arms 174,176 in the relaxed position interfere with boss member 130 from movingthrough space 175. To assemble the implant, the clips 170, and inparticularly the flexible, resilient arms 174, 176, are expanded to theexpanded position to permit the boss member 130 to slide over postmembers 150 and through space 175. In use, as the superior component 120moves relative to the inferior component, the boss member 130 alsomoves. When the distal end surface 134 of the boss member 130 moves pastthe top surface 173 of the clips 170, the resilient arms 174, 176 moveinward underneath the boss member 130. If an axial compression force isapplied to the spacer, the boss member will be supported by the clip 170and will not collapse to its original size. The individual clips 170 a,170 b, 170 c of the clip stacks 192, 194 may be circularly-shaped,C-shaped, V-shaped, U-shaped, Y-shaped or nearly any shape thatinteracts with the boss member and preferably accommodates the axialbore 123 extending through the spacer 110.

The endplates 122, 142 of the second embodiment of the interbody spacer110 also include a pin/slot mechanism 185 on each side of the expandableinterbody spacer 110 that preferably prevents overexpansion. Morespecifically, the inferior component includes tabs 190, one on eachside, that extend up from the inferior component toward the superiorcomponent. The tabs 190 include a slot 192. The boss member 120 includesa central section which preferably has two bores 194. When the inferiorcomponent and superior component are assembled, bore 194 aligns withslot 192 and a pin 195 is inserted through the bore 194 and slot 192.The pin 195 is permitted to slide in the slot 192 as the superior andinferior components move relative to each other until the pin 195contacts the ends of the slot 192 and acts as a stop mechanism 185 toprevent the spacer from disassembling. The spacer may have one or moretabs with slots, and corresponding bores and pins.

The footprint of the inferior and/or superior component of theexpandable interbody spacers 10, 110, 210 can be somewhat rectangular inshape, as shown in the first and second embodiments of FIGS. 1-6, or canbe curved, as shown in a third embodiment of the interbody spacer 210 ofFIGS. 7-8. Other shapes, configurations and sizes of the superior andinferior components, as well as shape, configuration and size ofexpandable spacer, are contemplated. In addition to the different shapesand sizes, the inferior and superior components of the spacers may haveone or more openings that may extend partially or entirely through thespacer for receiving grafting material to assist in fusing the bonebetween the vertebra. Furthermore, the spacers can use many differentconfigurations and arrangements of the clip members, bosses or bosselements, and post members.

Referring to FIGS. 9-11, an embodiment of an expandable interbodycorpectomy device 310 includes a single stack 390 of clips 370, a singleboss 330, and a single cylindrical protrusion 350. The expandableinterbody corpectomy device 310 also includes a housing 360 (shown inphantom in FIG. 9) that generally covers the moving parts of the device310 in the collapsed position and includes a window 365 (FIG. 10) toprovide access for actuation of the device 310.

The corpectomy device has a superior component 320 and an inferiorcomponent 340. The inferior component may comprise a portion of thehousing 360 and/or the protrusion 350. The protrusion 350 may beseparate from or integral with the inferior component 340, and may ormay not be secured to the inferior component 340. The housing 360,protrusion 350 and inferior component 340 may be an integral piece orall separate pieces, or a combination of integral pieces and separatepieces. The end faces or end plates 322, 342 of the superior andinferior components may be smooth as illustrated or may include a seriesof teeth, ridges, spikes, keels or surface texturing to assist withsecuring the corpectomy device 310 in position between vertebrae.

The corpectomy device 310 may be cylindrically shaped with circularlyshaped end faces 322, 342 as shown, or the corpectomy device 310 and endfaces 322, 342 may take any desirable shape, such as, for example, thoseillustrated in FIGS. 1-8, or other shapes. The end plates 322, 342 mayalso have openings 323, 343 (not shown), and the corpectomy device 310may have a generally hollow interior in order to pack the corpectomydevice 310 with bone grafting material during a procedure to assist inbone formation. The window 365 may communicate with the hollow interiorof the implant and the openings 323, 343 to assist in packing theimplant, spacer or corpectomy cage with bone grafting material.

The protrusion 350 and boss 330 are both shown as cylindrically shapedin FIGS. 9-11, but may have any desirable shape including, but notlimited to, the shapes and configurations shown in FIGS. 12-14. The clipstack 390 in the embodiment of FIGS. 9-11 has five clips, 370 a, 370 b,370 c, 370 c, and 370 e but may have more or less clips depending uponthe results desired. The clips 370 may be integral by a connectingmember or separate clips. The clips in the embodiment of FIGS. 9-11 iscircularly shaped with a slot, like an O-ring, but may also be anyshaped desired.

The corpectomy device 310 works in a manner similar to the embodimentsof FIGS. 1-8. In the fully expanded condition the distal end of the boss330 is positioned on top of the top surface of clip 370 e. Any force oraxial compression transmitted from a vertebrae to the superior surface322 of the corpectomy device is transmitted to the boss 330. The boss330 transmits the force to the stack 390 of clips 370 which transmitsthe force to the inferior component of the corpectomy device and to theinferior vertebrae. The corpectomy device would be implanted preferablyin its collapsed state. In the collapsed state, the protrusion 350 isinserted into the hollow space or recess of the boss 330, and the clips370 at least partially surround the exterior side surface of the boss330. The clips 370 surrounding the boss are preferably in their expandedstate where the arms of the clip are expanded or flexed outward topermit the boss to be inserted into the space defined by the arms of theclip.

As the corpectomy device is expanded the boss 330 moves relative to theclips 370. As the distal end 334 of the boss 330 moves past the topsurface 371 a of the first clip 370 a, the first clip 370 a returns toits relaxed position wherein the arms 374 a, 376 a of the clip 370 areturn to their non-expanded, non-flexed position (relaxed position) andmove underneath the boss 330. The boss 330 is then supported by thefirst clip 370 a and the corpectomy device 310 will retain the newheight which has been increased by the thickness of the clip 370 a. Iffurther height adjustment is desired the endplates are expanded whichmoves the boss 330 relative to the clips 370 until the distal endsurface 334 of the boss 330 moves past the top surface 371 b of clip 370b where upon the second clip 370 b returns to its relaxed position andthe arms of the clip 370 b move underneath the boss so that the clip 370b can support a load applied to the boss. The expansion of the implantmay continue until a desired height is reached and in this manner thecorpectomy device 310, like the vertebral spacers 10, 110, 210, arestep-wise incrementally adjustable to different sizes in predefinedincrements.

Further illustrations of expandable corpectomy devices and designcomponents are shown in FIGS. 12-14. Specifically, FIGS. 12-14 disclosethe clip stack 70′ having an integral spine 72′ that joins theindividual clips. The clip stack 70′ may be formed of a single piece ofmaterial where slots or grooves 97 are formed in the material to formthe separate clips which remain integrally connected. The grooves mayalso include relief radius sections 98 at the end of the groove 97. Thestack 70′ may further include a recess 99 to assist with the flexibilityof the clips.

The clips may take other shapes and configurations other thanillustrated in FIGS. 1-14. For example, the clips may take the shapeshown in FIG. 15 which is basically an open ended rectangular or U-shapewhere arms 74′″, 76′″ can expand or flex between the relaxed position inFIG. 15 and the expanded position shown in FIG. 18. The boss 30′ asshown in FIGS. 16 and 17 would also be an open ended rectangular shapeor U-shape where extensions 31′ would fit within the space 75′″ formedby the arms 74′″, 76′″, when the arms are in the expanded position.

As shown in FIG. 18, the boss member 430 in the implant, spacer orcorpectomy device may be configured so that it at least partiallysurrounds the clip members 470 or clip stack 490 when the implant,spacer or corpectomy device is in the collapsed or non-fully-expandedposition. The clips 470 in FIG. 18 in their relaxed condition or stateare sized to interfere with movement of the boss member. That is in therelaxed condition the boss 430 can not fit over or around the clipmembers. In the embodiment of FIG. 18, the clips 470 b, 470 c, 470 d arecontracted so that the arms 474, 476 of the clip are closer together topermit the boss 430 to move over and partially surround or overlap theclip member. As the boss member 430 moves relative to the clip memberand the end surface 434 of the boss member 430 moves past the endsurface 471 a of the clip member 470 a, the arms 474 a, 476 a of theclip member expand to a position underneath of and in support of theboss 430. The implant, spacer or corpectomy device may be configured ineither manner so that the clip members may be expanded or alternativelycontracted so that the clip members do not interfere or block movementof the boss member.

While the boss members, the post elements and protrusions, clip membersand clip stacks have been shown as generally straight and which permitstraight axial movement, the boss members, post or protrusion members,clip members and/or the clip stacks may be curved so that the implant,spacer or corpectomy device endplates or faces can be angled withrespect to each other. Alternatively or additionally, the clip membersmay have non-uniform thickness or curves so that the endplates of theimplant may be angled with respect to each other. These features mayassist in restoring proper alignment of the vertebrae and may restore alordotic curve or a kyphotic curve.

FIG. 19 illustrates an embodiment of a radially, mechanical ratcheting,expandable interbody spacer or expandable corpectomy device 500.

FIGS. 20-22 illustrates an embodiment of a mechanical, expandableinterbody spacer device 510 that includes oppositely facing upper andlower endplates 622, 642 disposed around a shaft 616 that preferably hasan elliptical camming surface 618. The shaft 616 further includes a gear620 on one end that can interface with a feature extending from one orboth of the endplates 622, 642. Starting from a collapsed position inFIGS. 20 and 21, as the shaft 616 and gear 620 are rotated, the cammingsurface 618 pushes the endplates 622, 642 apart in the cranial/caudaldirection, thereby moving the device 610 to an expanded position shownin FIG. 22. Once the desired height of the device 610 is obtained, thegear 620 is pushed inwardly and engages an interface feature (not shown)to lock the desired height, such as between 6 mm and 18 mm. Thedescribed height range of between 6 mm and 18 mm is not limiting and thedevice 610 may be expanded to a variety of different heights, dependingupon the anatomy of the patient receiving the implant/device 610,preferences of the surgeon and related factors.

FIG. 23-24 illustrates another embodiment of an expandable interbodyspacer 710 that includes a pair of oppositely facing endplates 722, 742,each of which further include a ridged rack 756 that runs in thecranial/caudal direction. The endplates 722, 742 are preferably disposedwithin a body 758 via a plurality of cylindrical bosses 760. Within thebody 758 there is preferably included a shaft 782 that further includesgears 762 on either end and is disposed at the center of the expandableinterbody spacer 710. Disposed on either of the gears 762 is adepression 762 a that is formed to allow torque to be applied to theshaft via an instrument (not shown). In a fully collapsed condition,either gear 762 is urged to rotate as far as possible in a firstdirection to move the spacer 710 from a collapsed position (FIG. 23) toan expanded position (FIG. 24). A central gear 763 is disposed at thecenter of the expandable interbody spacer 710 and is mounted to theshaft. The central gear 763 preferably interfaces with the ridged racks756 as a tool interfaces with and applies torque to the shaft throughone or both of the gears 762. When the tool rotates the shaft 782 in asecond direction, the central gear 783 causes the endplates 722, 742 toexpand in the cranial/caudal direction by translating the ridged gear.Once a desired height is obtained, one of the gears 762 preferablyengages a feature on the implant body 758 to lock the shaft from furtherrotation. For example, spring loaded stops 764 may be mounted to thebody 758 to lock the shaft 782 and gears 762 in position to set thedesired height.

FIGS. 25-27 illustrate a further embodiment of a mechanical, expandableinterbody spacer 810 that includes a pair of oppositely facing endplatecomponents 822, 842, each of which are attached to a link 806 on eitherside of the expandable interbody spacer 810 with a pin 808. Theexpandable interbody spacer 810 further includes two blocks 812, 815disposed between the endplates 822, 842, preferably at opposite endsfrom one another. The blocks 812, 815 are preferably connected to oneanother by a screw 814, but are not so limited and may be connected toeach other with nearly any mechanism that permits urging of the blocks812, 815 toward and/or away from each other, as will be describedfurther below. A spring 816 preferably surrounds the shaft of the screw814 between the two blocks 812, 815. In a fully collapsed position (FIG.26), the blocks 812, 815 are positioned in relatively close proximity toeach other. A tool engages the screw 814 and is used to turn the screw814 at the posterior end of the expandable interbody spacer 810. As thescrew 814 is rotated the blocks 812, 815 move toward each other, therebyforcing the links 806 to orient themselves more vertically and theendplates 822, 842 to move away from each other. As the links 806 shift,they push the endplates 822, 842 in the cranial/caudal direction.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. For example, the features and configurationscan be applied singularly or in combination and the boss elements, clipmembers may take on an number of different shapes and configurations,and the implant, spacer or corpectomy device may optionally include postmembers, or optionally stop mechanisms to prevent disassembly. While theembodiments disclosed have been referred to as spacers or corpectomydevices, the present invention is not so limited to such implant devicesand may be referred to by different terms, and may be used in otherparts of the body besides the spine and in non-medical applications. Itis understood, therefore, that this invention is not limited to theparticular embodiments disclosed, but it is intended to covermodifications within the spirit and scope of the present invention asdefined by the appended claims.

We claim:
 1. A method for restoring space between two adjacentvertebrae, the method comprising: providing an expandable interbodyspacer capable of having a collapsed condition and expanded condition,the spacer comprising: a superior component having an external surfacefor contacting at least a portion of one of the adjacent vertebrae, aninferior component having an external surface for contacting at least aportion of the other adjacent vertebrae, wherein the superior andinferior components are moveable relative to each other so that thespacer may move between the collapsed condition and the expandedcondition; at least one boss member positioned between and moveablerelative to at least one of the superior component and inferiorcomponent, the boss member including a side surface and a distal endsurface; and a plurality of expandable clip members, each clip memberhaving a top surface, a relaxed position, a deflected position, and aspace, wherein the boss member is arranged and configured to passthrough the space when the clip member is in the deflected position andthe clip member interferes with the movement of and does not permit theboss member to pass through the space when the clip member is in therelaxed position, each of the clip members being in the deflectedposition when the spacer is in the collapsed condition; inserting thespacer into a cavity of a vertebral column, wherein the cavity isdefined by an intervertebral disc space or a space in a vertebral body;expanding the spacer from the collapsed condition to the expandedcondition by moving the superior component of the spacer relative to theinferior component of the spacer such that the distal end surface of theboss member passes a top surface of at least one of the plurality ofclip members such that the at least one clip member moves from thedeflected position to the relaxed position, wherein moving the superiorcomponent relative to the inferior component deflects the clip membersin a series to the relaxed position and allows the spacer to expand inpredefined increments, wherein the expansion of the spacer provides acorrection to the vertebral column; and determining the total correctionmade to the vertebral column by the expansion of the spacer.
 2. Themethod of claim 1 wherein, each clip member is stacked one on top of theother to form at least one stack of clip members.
 3. The method of claim2 the method further comprising: adjusting the height of the spacer byincrementally expanding the spacer by moving the superior component ofthe spacer relative to the inferior component of the spacer such thatthe distal end surface of the boss member passes a top surface of eachof the clip members, wherein each clip member moves from the deflectedposition to the relaxed position as the boss member passes a top surfacethereof as the spacer expands.
 4. The method of claim 2 wherein thespacer further comprises more than one stack of clip members, each stackcomprising a plurality of clip members.
 5. The spacer of claim 1 whereinthe clip members have integral resilient and elastically deflectablearms that move upon application of a force.
 6. The method of claim 1wherein the superior component of the spacer includes at least one bossmember extending from the superior component toward the inferiorcomponent, and the inferior component of the spacer includes a postmember extending from the inferior component toward the superiorcomponent, wherein the post member is associated with the boss membersuch that the post member may telescope with respect to the boss memberas the implant expands and collapses.
 7. The method of claim 1 whereinas the spacer is expanding, the clip members move to a relaxed positionunderneath the boss member as the distal end of the boss member passesthe top surface of the clip member and supports the superior componentwhen subjected to axial compression.
 8. The method of claim 1 whereinthe spacer further comprises a stop mechanism to limit the expansion ofthe spacer.
 9. The method of claim 1 the method further comprisinginserting a distractor to move the superior component relative to theinferior component to expand the spacer from the collapsed condition tothe expanded condition.
 10. The method of claim 1 wherein the spacerfurther comprises a housing that covers the spacer, wherein the housingcomprises a window for access to the spacer.
 11. The method of claim 10the method further comprising inserting grafting material into thespacer through the window of the housing.
 12. A method for restoringspace between two adjacent vertebrae, the method comprising: providingan expandable interbody spacer capable of having a collapsed conditionand expanded condition, the spacer having: a superior component havingan external surface for contacting at least a portion of one of theadjacent vertebrae, an inferior component having an external surface forcontacting at least a portion of the other adjacent vertebrae, whereinthe superior and inferior components are moveable relative to each otherso that the spacer may move between the collapsed condition and theexpanded condition; a plurality of boss members positioned between andmoveable relative to at least one of the superior component and interiorcomponent, the boss members including a side surface and a distal endsurface; a plurality of expandable clip members forming a plurality ofstacks of clip members, each clip member having a top surface, a relaxedposition, a deflected position, and a space, wherein the boss membersare arranged and configured to pass through the space when the clipmembers are in the deflected position and the clip members interferewith the movement of and do not permit the boss members to pass throughthe space when the clip members are in the relaxed position, each of theclip members being in the deflected position when the spacer is in thecollapsed condition; and a housing that covers the spacer, wherein thehousing comprises a window for access to the spacer; inserting thespacer, into a cavity of a vertebral column, wherein the cavity isdefined by an intervertebral disc space or a space in a vertebral body;expanding the spacer from the collapsed condition to the expandedcondition by moving the superior component of the spacer relative to theinferior component of the spacer such that the distal end surface of theboss members passes a top surface of at least the clip members such thatthe at least one clip member moves from the deflected position to therelaxed position, wherein moving the superior component relative to theinferior component deflects the clip members in a series to the relaxedposition and allows the spacer to expand in predefined increments,wherein the expansion of the spacer provides a correction to thevertebral column; and determining the total correction made to thevertebral column by the expansion of the spacer.
 13. The method of claim12 the method further comprising inserting grafting material into thespacer through the window of the housing.
 14. The method of claim 12wherein the clip members have resilient arms that expand uponapplication of a force.
 15. The method of claim 14 wherein the pluralityof stacked resilient clips form at least two separate stacks of clipmembers, each stack of clip members associated with a different bossmember.
 16. The spacer of claim 15 wherein the superior and inferiorcomponents include edges along their perimeter, the separately stackedclip members located between the boss members and perimeter edges of thesuperior and inferior components.
 17. The method of claim 12 the methodfurther comprising: adjusting the height of the spacer by incrementallyexpanding the spacer by moving the superior component of the spacerrelative to the inferior component of the spacer such that the distalend surface of the boss member passes a top surface of each of the clipmembers, wherein each clip member moves from the deflected position tothe relaxed position as the boss member passes a top surface thereof asthe spacer expands.
 18. The method of claim 12 wherein as the spacer isexpanding, the clip members move to a relaxed position underneath theboss member as the distal end of the boss member passes the top surfaceof the clip member and supports the superior component when subjected toaxial compression.
 19. A method for restoring space between two adjacentvertebrae, the method comprising: providing an expandable interbodyspacer capable of having a collapsed condition and expanded condition,the spacer comprising: a superior component having an external surfacefor contacting at least a portion of one of the adjacent vertebrae, aninferior component having an external surface for contacting at least aportion of the other adjacent vertebrae, wherein the superior andinferior components are moveable relative to each other so that thespacer may move between the collapsed condition and the expandedcondition; at least one boss member positioned between and moveablerelative to at least one of the superior component and inferiorcomponent, the boss member including a side surface and a distal endsurface; and a plurality of expandable clip members, each clip memberhaving a top surface, a relaxed position, a deflected position, and aspace, wherein the boss member is arranged and configured to passthrough the space when the clip member is in the deflected position andthe clip member interferes with the movement of and does not permit theboss member to pass through the space when the clip member is in therelaxed position, each of the clip members being in the deflectedposition when the spacer is in the collapsed condition; a housing thatcovers the spacer, wherein the housing comprises a window for access tothe spacer; inserting the spacer into a cavity of a vertebral column,wherein the cavity is defined by an intervertebral disc space or a spacein a vertebral body; expanding the spacer from the collapsed conditionto the expanded condition by moving the superior component of the spacerrelative to the inferior component of the spacer such that the distalend surface of the boss member passes a top surface of at least one ofthe clip members, such that the at least one clip member moves from thedeflected position to the relaxed position, wherein moving the superiorcomponent relative to the inferior component deflects the clip membersin a series to the relaxed position and allows the spacer to expand inpredefined increments, wherein the expansion of the spacer provides acorrection to the vertebral column; determining the total correctionmade to the vertebral column by the expansion of the spacer; andinserting grafting material into the spacer through the window of thehousing.